Al vs HP vs LP tank questions

[littlejohn]

Been looking at getting 2 tanks (Nitrox) 100cf

Looking at all the numbers I dont see any problems is tank size as I am 6'4"

Questions that I have are dealing with wether to go HP - LP - AL and that +10% bit
Looking at some of the tables some tanks cf rating is including the 10% and some are not.

If the HP 100 takes 3442# + 10% that comes out to 3786#
And the AL 100 takes 3300# + 10% that comes out to 3630#
With the LP 100 taking 2460# +10% that comes out to 2700#

I would expect any LDS to be able to fill to 3000# -But how hard is it to get a fill above 3500#

Are tanks with an 8" dia that much of a problem?
And by the looks of things online a lot of sites arn't even listing the LP tanks

 

[PerroneFord]

Well,

Aluminum tanks and HP tanks do not get the 10% overfill. That is strictly a LP tank deal. So a HP100 will have 100cuft of gas at 3442, and the AL100 will have 100cuft at 3300. Most dive shops here in N.FL. have no trouble filling to those pressures, but you might find some issue at small shops or "vacation" shops in other areas.

The LP tanks are nice because you can easily get a full fill just about anywhere, and many shops will put 3000psi into the tanks anyway (just like an AL80) giving you a nice boost. The LP steel tanks are cheaper than the HP steel tanks. The LP steel tanks often have favorable buoyancy characteristics which is why they are favored amongst technical divers.

8" diameter tanks are favored by many groups, especially your cave diving cousins up here to your north.

 

[DA Aquamaster]

LP tanks are declining in number and use, mostly because a 3442 psi tank of a given external dimension and weight has a capacity similar to or very close to an LP tank of the same external dimensions. So in effect E series 3442 psi tanks are kinda like LP tanks that you can legally overfill to a lot more volume for the given weight and size - which pretty much eliminates the need for LP tanks.

In more understandable and practical terms, an E series 130 cu ft tank will hold 100 cu feet at 2640 psi and a 120 cu ft E series tank will hold about 92 cu ft at 2640 psi. At 3000 psi the 130 holds 113 cu ft and the 120 holds 104, so getting less than full fills is not really an issue for anything other than the 100 cu ft E series tank.

So if it were me, I'd compare the weights and sizes of the 120 and 130 cu ft PST E series and the nearly identical Worthington X series tanks to the 100 cu ft LP tanks you are considering and see what gives you the most bang for a given weight and size.

Bouyancy traits for steels vary some what with some Faber models being comparatively negative (around -7 or -8 lbs empty) and most other 3442 psi steel tanks being a couple pounds negative when empty.

AL 100's are also close to the positive side of neutral but are larger and heavier than their steel counterparts and their 3442 psi steel counterparts in particular. They are comparatively inexpensive, but have no other attractive quality compared to a steel (IMHO).

HP tanks are normally consiudered to be a true 3500 psi tank, and those are also becoming less common due to some fairly pointless conventions requiring a 300 bar DIN valve at 3500 psi when a 232 bar DION/K valve is considered to be just fine at 3442 psi.

 

[Jimmer]

Have you or do you have the opportunity to dive any of these tanks? IMHO the AL100 is rather big and unwieldy, and I didn't particularly care for it. The HP100 is a breeze to dive, and the LP100 (presumably LP95 or 98) is the same height as the 100, but a little fatter, and I quite like that tank. My suggestion would be to dive them all if possible, and if the LP95 or 98 suits you, then I would buy an HP119, which is the same physical size and weight for all intents and purposes, but has 20% more gas since it fills to higher pressure. Even if you get a short fill, you'll still end up with more than 100 CF of gas.

Jim

 

[Colliam7]

Been looking at getting 2 tanks (Nitrox) 100cf . … Looking at all the numbers I dont see any problems is tank size as I am 6'4"

Agreed, you could probably use long tanks (e.g. HP 120s) or short tanks with equal ease.

I would expect any LDS to be able to fill to 3000# -But how hard is it to get a fill above 3500#

That really depends on the location. There are more than a few shops and dive centers out there who will fill to 3000 but can’t fill to 3500. But, a 3000 psi fill on a 3442 HP 119 is still, as noted, a bit over 100cf. Those that can fill to 3500 may be able to slightly overfill the HP3442s – not by 10% but by a 100psi or so.

Are tanks with an 8" dia that much of a problem?

No.

LP tanks are declining in number and use, mostly because a 3442 psi tank of a given external dimension and weight has a capacity similar to or very close to an LP tank of the same external dimensions.

Good point. You will see more HP than LP going forward.

Have you or do you have the opportunity to dive any of these tanks? IMHO the AL100 is rather big and unwieldy, and I didn't particularly care for it. The HP100 is a breeze to dive, and the LP100 (presumably LP95 or 98) is the same height as the 100, but a little fatter, and I quite like that tank. My suggestion would be to dive them all if possible, and if the LP95 or 98 suits you, then I would buy an HP119

Another good point. If you can dive some different tanks before buying, by all means do so! I dive HP120s, at 5’11” – both single and double, and they are fine, albeit a bit long. I don’t care for AL100s, either. HP 130s are fine. But, I am looking at 119s – they are just very comfortable tanks.

 

[Scared Silly]

I would agree that the new HP are in general similar to LPs when comparing the volume of gas at similar pressures (within 10%). However, the HP are slightly heavier both dry and wet. When diving them as singles it is not that much of a difference but once doubled up the difference can be significant. Given that it appears the OP is looking for singles this is moot but when looking at cylinders one should look at all of the characteristics - I think dry weight and buoyancy are often over looked. There are some cylinders that are bricks just there are some that are bobs.

 

[captndale]

If the HP 100 takes 3442# + 10% that comes out to 3786#
And the AL 100 takes 3300# + 10% that comes out to 3630#
With the LP 100 taking 2460# +10% that comes out to 2700#

I think that if you check the tank specifications you will find that the pressure ratings of the tanks you list are off.

HP tanks rated at 3442 are not allowed to be overfilled by 10%.
Aluminum tanks, likewise, cannot receive a + rating.
Low Pressure steel tanks are rated at a nominal 2400 psi. At a 10% overfill that comes to 2640 psi.

 

[Otter]

Just a clarification (hopefully not redundant), a LP 95 is ONLY 95 cu ft with the 10% (2640 PSI) over fill. At each hydro, the plus rating may/may not be given again meaning that your LP 95 drop to 2400/2640ths of 95 or 86.4 cu ft -- assuming the filler actually follows the rating.

 

[Nemrod]

I have a plus stamp.


It has been my general experience that I do not care for most HP tanks. They tend to be awfully negative and top heavy.

This is a nice chart that some will find useful for selecting tanks to suit their needs whatever they maybe.:

Scuba Cylinder Specification Chart from Huron Scuba, Ann Arbor Michigan

edit to add useful link.

N

 

[mikeguerrero]

The faber 100's that I have dove are + series and are extremely heavy, far heavier than my brand new set of XS scuba HP 100's by Worthington. In my experience a much lighter and better tank.

MG